1. Field of the Invention
Embodiments of the present invention relate to a method of removing an oxide and a method of filling a trench using the same. More particularly, embodiments of the present invention relate to a method of removing a portion of an oxide layer and a method of filling a trench using the same without forming voids and/or seams therein.
2. Description of the Related Art
Semiconductor devices may require high speed and large storage capacity in order to provide proper functioning. Accordingly, a method of manufacturing the semiconductor devices may require forming semiconductor devices with high density, reliability, and response speed. A conventional method of manufacturing semiconductor devices may include formation of a device isolation region, i.e., a region determining a size of an active region of a semiconductor device and a margin thereof, in a substrate, so electrical components, e.g., a diode, a transistor, and so forth, may be formed in the active region of the substrate.
A conventional device isolation process may include a thermal field oxidation process, e.g., a local oxidation of silicon (LOCOS) process. In a conventional LOCOS process, oxide and nitride layers may be formed sequentially on a substrate, followed by patterning of the nitride layer to form an anti-oxidation mask. The anti-oxidation mask may be used to selectively oxidize the substrate to form a field oxide layer, i.e., device isolation, thereon. However, the conventional LOCOS process may cause penetration of the oxide layer through peripheral portions of the anti-oxidation mask, thereby causing formation of a bird's beak at peripheral portions of the field oxide layer. As such, the field oxide layer may overlap an active region of the substrate, thereby reducing a width of the active region and degrading electrical characteristics thereof.
Another example of a conventional device isolation process may include a shallow trench isolation (STI) structure. A conventional STI structure may include deposition of an oxide layer inside a trench formed in a semiconductor substrate, followed by wet etching or plasma etching to remove a portion of the oxide layer. However, an increased integration of the semiconductor device may require a reduced size of the active/field regions, thereby requiring an increased aspect ratio of the trench, i.e., a ratio of width to depth. Deposition of an oxide layer in a trench having a high aspect ratio may be difficult and non-uniform, so voids and/or seams may be formed in the oxide layer inside the trench.
For example, if high density plasma chemical vapor deposition (HDP-CVD) is used to form the oxide layer in the trench, deposition and sputtering may be performed at the same time. Accordingly, the oxide layer deposited in an upper portion of the trench may be sputtered and reattached, thereby causing non-uniform deposition. In other words, since a deposition speed of the oxide layer in a vertical direction may be faster than a deposition speed of the oxide layer in a horizontal direction, voids and/or seams may be formed in the oxide layer inside the trench. Attempts have been made to minimize formation of voids and/or seams in an oxide layer formed via a HDP-CVD by using a hydrogen gas. However, use of the hydrogen gas may cause an active pitting phenomenon, i.e., local pitting of an active region, thereby triggering defective operation of a unit device corresponding to the active region. Such defective operation may decrease reliability and production yield of the semiconductor device.
Further, use of wet etching or plasma etching to remove a portion of the oxide layer from the trench in a conventional STI structure process may cause excessive etching, thereby causing damage to the semiconductor device. Attempts have been made to minimize excessive damage by using a liner or reducing RF power. However, such methods may degrade gap-fill ability of the oxide layer in the trench, thereby increasing voids and/or seams in the oxide layer inside the trench.